Liquid crystal displaying has dominated the flat panel displaying field for its advantages of stable picture, realistic image, less radiation, space and energy saving. Typically, a liquid crystal device includes a back light module and a liquid crystal display panel on which a plurality of scanning lines and data lines crossing with each other are provided. The scanning lines and the data lines extend to the edge of the display panel to form wirings for coupling with external circuit board(s). For the large number of scanning and data lines, it is difficult for soldering them by a conventional technique. Typically, flexible chip on film bonding technique is used for wire bonding, i.e., a method of heat pressing and attaching is used to attach and fix the conductive terminals of the scanning and data lines and the COF flexible circuit board by anisotropic conductive adhesive, namely anisotropic conductive film (ACF).
A conventional COF flexible circuit board is illustrated in FIG. 1, which substantially includes: a substrate; a plurality of conductive terminals 1 arranged separately in parallel on the substrate, wherein each of the terminals 1 includes a wide line 2 and a narrow line 3; and an anisotropic conductive adhesive region 4. The anisotropic conductive adhesive contains conductive particles therein. After the attachment of the COF flexible circuit board and the glass substrate by heat pressing, the gap between the terminals 1 and the wires are the thinnest, and the anisotropic conductive adhesive therebetween is pressed so that the conductive particles between the wires and the terminals 1 are compressed to deform to contact against each other, thereby forming a conductive path, which has one end contacting the wires and another end contacting the conductive terminals 1, and an electrical coupling between the wires and the conductive terminals 1 is formed. Since the gaps between the wires and between the terminals are relatively wide, the conductive particles are in a loose state to be substantially isolated from each other, short circuit between two adjacent wires or terminals 1 is avoided, which improves the stability of electrical coupling or connection.
A major problem of the conventional COF flexible circuit board is that it is easily broken. Since the COF flexible circuit board needs to be bent frequently, it occurs frequently that the COF flexible circuit board is broken or damaged, resulting in undesirable phenomena such as open circuit. A typical method of reducing the possibility of the COF flexible circuit board being broken in the art is by careful operation of the operator, or by using an automatic chuck to prevent the COF circuit board per se to be bent frequently. But bent by force is only one of the extrinsic factors causing the COF flexible circuit board to be broken, the essential reasons for the COF flexible circuit board being easily broken is that the resistance to breakage of the circuit board is not strong.